1. Field of the Invention
The field of the invention is mixing valves for mixing two fluids together in variable accurate proportions.
2. Description of the Prior Art
The oxygen binding curve of blood is a plot of the oxygen concentration of the atmosphere to which the blood is exposed against the resulting optical properties of the blood. It is understood that blood which is well oxygenated is reddish, while blood which is lacking in oxygen is bluish.
The shape of the oxygen binding curve is of substantial physiological and clinical significance, as it furnishes information on the oxygen transport ability and health of the blood.
In the prior art it has been common to expose the blood sample in a chamber to an atmosphere which is varied by initially filling the test chamber with one gas, say nitrogen, inserting the sample, and then purging the chamber with the other gas, say oxygen. Instrumentation, responsive to oxygen concentration in the chamber, controls the X axis of a plotter while optical means, sensing the blood properties, controls the Y axis of the plotter.
By means of the mixing valve disclosed in U.S. Pat. No. 3,980,102 it is possible to directly and accurately control the oxygen concentration in the test chamber in a mechanical way, rather than indirectly by purging and measuring the resulting concentration. Furthermore, the movement of the mechanical control means is linearly related to the oxygen concentration achieved, so that it is simple to control the X axis of the plotter in accordance with said movement.
The mixing valve disclosed hereinafter is related to the mixing valve disclosed and claimed in U.S. Pat. No. 3,980,102 issued to this applicant on Sept. 14, 1976. In this prior patent there is disclosed a mixing valve which functions in the manner described above and which has a rectangular base and a rectangular slide member which cooperates with the base. As will be described hereinafter in greater detail the mixing valve of the present invention proposes a rotatable core in place of the base and a cylindrical housing in place of the slide member.